What is radon? Element of the 18th group of the periodic system of chemical elements DI Mendeleyev

In the light of the rapid development of science and technology, specialists express concern about the lack of propaganda of radiation hygiene among the population. Experts predict that in the next decade "radiological ignorance" can cause a real threat to the security of society and the planet.

The Invisible Assassin

In the XVth century, European medical professionals stalled the abnormally high mortality from lung diseases among workers in mines that produce iron, polymetals and silver. Mysterious disease, called "mountain sickness," hit miners fifty times more often than the average inhabitant. Only at the beginning of the 20th century, after the discovery of radon, it was recognized as the reason for stimulating the development of lung cancer of miners in Germany and the Czech Republic.

What is radon? Is it only a negative influence on the human body? To answer these questions, one should recall the history of the discovery and study of this mysterious element.

Emanation - means "flow"

The discoverer of radon is considered to be the English physicist E. Rutherford. It was he who, in 1899, noticed that thorium-based preparations, in addition to heavy α-particles, emit a colorless gas, leading to an increase in the level of radioactivity in the environment. The researcher called the alleged substance the emanation of thorium (from emanation (lat.) - expiration) and assigned him the letter designation Em. Similar emanations are also found in radium preparations. In the first case, the emitting gas was called thoron, in the second - radon.

Later it was possible to prove that gases are radionuclides of a new element. It was the first time a Scottish chemist, a Nobel laureate (1904), William Ramsay (with Whitlow Gray), succeeded in isolating it in pure form in 1908. Five years after the element, the name Radon and the symbolic designation Rn were finally fixed.

What is radon?

In the periodic system of chemical elements of DI Mendeleev radon is in the 18th group. Has an atomic number z = 86.

All existing isotopes of radon (more than 35, with mass numbers from 195 to 230) are radioactive and represent a certain danger to humans. In nature, there are four types of elemental atoms. All of them are part of the natural radioactive series of actinurane, thorium and uranium-radium. Some isotopes have their own names and, according to a historically established tradition, they are called emanations:

• Actinium - actinone ²¹⁹ Rn;
• Thorium - thoron ²²⁰ Rn;
• Radium - radon ²²² Rn.

The latter is the most stable. The half-life of radon ²²² Rn is 91.2 hours (3.82 days). The steady state of the remaining isotopes is calculated in seconds and milliseconds. When decay with the emission of α particles, the formation of polonium isotopes takes place. By the way, it was during the study of radon that scientists first encountered numerous types of atoms of the same element, which later were called isotopes (from the Greek "equal", "identical").

Physical and chemical properties

Under normal conditions, radon is a gas without color and odor, the presence of which can only be determined by special devices. The density is 9.81 g / l. It is the heaviest (air is 7.5 times lighter), the rarest and most expensive of all known gases on our planet.

It is readily soluble in water (460 ml / l), but in organic compounds the radon solubility is an order of magnitude higher. Has the effect of fluorescence, caused by high self-radioactivity. For the gaseous and liquid state (at a temperature below -62 ° C) there is a blue glow, for a crystalline (below -71 ° C) - yellow or orange-red.

The chemical characteristic of radon is due to its belonging to a group of inert ("noble") gases. It is characterized by chemical reactions with oxygen, fluorine and some other halogens.

On the other hand, the unstable core of the element is a source of high-energy particles that affect many substances. The effect of radon leads to the staining of glass and porcelain, decomposes water into oxygen, hydrogen and ozone, destroys paraffin and petrolatum, etc.

Getting radon

To separate radon isotopes, it is sufficient to pass a jet of air over a substance containing radium in one form or another. The concentration of gas in the jet will depend on many physical factors (humidity, temperature), on the crystal structure of the substance, its composition, porosity, homogeneity and can range from small fractions to 100%. Usually, solutions of bromide or chloride radium in hydrochloric acid are used. Solid porous substances are used much less often, although radon is more pure.

The resulting gas mixture is purified from water, oxygen and hydrogen vapor, passing it through a hot copper grid. The remainder (1/25000 of the original volume) is condensed with liquid air and contaminants of nitrogen, helium and inert gases are removed from the condensate.

For the record: in the whole world only a few tens of cubic centimeters of the chemical element of radon is produced per year.

Distribution in nature

Radium nuclei, the product of which is radon, are in turn formed during the decay of uranium. Thus, the main source of radon is the soils and minerals containing uranium and thorium. The highest concentration of these elements in magmatic, sedimentary, metamorphic rocks, dark-colored schists. Gas radon, due to its inertness, easily leaves the crystal lattices of minerals and, through the voids and cracks in the earth's crust, easily spreads over long distances, emerging into the atmosphere.

In addition, the ground inter-layer waters, washing such rocks, are easily saturated with radon. Radon water and its specific properties were used by man long before the discovery of the element itself.

Friend or foe?

Despite thousands of scientific and popular scientific articles written about this radioactive gas, one can unequivocally answer the question: "What is radon and what is its significance for humanity?" Seems difficult. Before modern researchers there are, at least, two problems. The first is that, in the sphere of radon radiation exposure to living matter, it is both a harmful and useful element. The second - in the absence of reliable means of registration and monitoring. The existing radon detectors in the atmosphere, even the most modern and sensitive ones, can produce results that are several times different when the measurements are repeated.

Be careful, radon!

The main dose of radiation (more than 70%) in the process of life activity is due to natural radionuclides, among which the leading positions belong to radiant gas. Depending on the geographical location of the residential building, its "contribution" can be from 30 to 60%. The constant amount of unstable isotopes of a hazardous element in the atmosphere is maintained by continuous intake from terrestrial rocks. Radon has an unpleasant property to accumulate inside residential and public premises, where its concentration can increase tens and hundreds of times. For human health, the danger poses not so much the radioactive gas itself as the chemically active isotopes of polonium ²¹⁴ Po and ²¹⁸ Po, formed as a result of its decay. They are firmly retained in the body, damagingly affecting the internal α-radiation on living tissue.

In addition to asthmatic attacks of suffocation and depression, dizziness and migraine, it is fraught with the development of lung cancer. The risk group includes workers of uranium mines and ore-dressing plants, volcanologists, radon therapists, the population of unfavorable areas with a high content of radon derivatives in the earth's crust and artesian waters, radon resorts. To identify such areas, maps of radon hazard are used, applying geological and radiation-hygienic methods.

For the note: it is believed that it was irradiation with radon that provoked the death from lung cancer in 1916, the Scottish explorer of this element, William Ramsay.

Ways of protection

In the last decade, following the example of the western neighbors, the necessary anti-radon measures began to spread in the countries of the former CIS. There were normative documents (SanPin 2.6.1., SP 2.6.1.) With clear requirements for ensuring radiation safety of the population.

The basic measures to protect against soil gases and natural radiation sources include:

• Arrangement on the earth floor of the wooden floors of a monolithic concrete slab with crushed stone and reliable waterproofing.
• Providing increased ventilation of the basement and basement space, airing of residential buildings.
• Water entering kitchens and bathrooms must be filtered, and the premises themselves must be equipped with compulsory exhaust devices.

Radiomedicine

What is radon, our ancestors did not know, but even the glorious horsemen of Genghis Khan healed their wounds with the waters of the sources of Belokurikha (Altai), saturated with this gas. The fact is that in micro doses radon has a positive effect on the vital organs of man and the central nervous system. The impact of radon water accelerates metabolic processes, due to which damaged tissues are restored much faster, the work of the heart and the circulatory system is normalized, the walls of the vessels are strengthened.

The resorts of the mountain regions of the Caucasus (Essentuki, Pyatigorsk, Kislovodsk), Austria (Gastein), Czechia (Jáchymov, Karlovy Vary), Germany (Baden-Baden), Japan (Misasa) have long been deservedly famous and popular. Modern medicine, in addition to radon baths, offers treatment in the form of irrigation, inhalation under the strict supervision of the appropriate specialist.

At the service of mankind

The scope of the radon gas is not limited to medicine alone. The ability of element isotopes to adsorption is actively used in materials science to measure the degree of heterogeneity of metal surfaces and decoration. In the production of steel and glass, radon serves to control the flow of technological processes. With its help, check the gas masks and chemical protection means for leaks.

In geophysics and geology, many methods of searching for and detecting deposits of minerals and radioactive ores are based on the application of radon photography. By the concentration of radon isotopes in the soil, it is possible to judge the gas permeability and density of mountain formations. Monitoring of the radon situation looks promising in terms of predicting the upcoming earthquakes.

It remains to be hoped that with the negative effects of radon humanity will still cope and the radioactive element will only bring benefit to the population of the planet.